354 THE WHEAT PLANT 



The grains from single ears of each of the 36 " sported " plants were 

 sown separately, the range of the forms of the ears of their progeny being 

 illustrated in line B. In addition to the morphological characters already 

 mentioned, plants with fully-bearded ears appeared in this generation. 

 Examples such as this, if they are cases of Mendelian segregation, involve 

 several pairs of allelomorphic characters. 



Some varieties of wheat which have remained constant for a con- 

 siderable period suddenly give rise to one or more sports. 



These cases I regard as hybrids, which are stable under one set of 

 climatic and soil conditions, but have been induced to sport by cultivation 

 in a new environment. Examples which I consider support this 

 view, I observed in two pedigree cultures of Huguenot wheat a peculiar 

 beardless form of T. durum (Fig. 146), selected from a crop of Medea 

 (T. durum) about 1898 by J. Currell of Arthur River, Western Australia, 

 and supposed to be a hybrid between Medea and Purple Straw (a 

 vulgar e wheat). 



For four years two short rows of 10-12 plants of each culture were 

 raised at Reading annually from single ears of the previous season. These 

 showed no variation until the fifth year, when both cultures sported in the 

 same manner, giving fully-bearded, semi-bearded, and beardless plants 

 of T. durum ; the numbers of each, however, were too small to admit of 

 any reliable ratios being established. 



It may be argued that such an example, like those already mentioned, 

 is merely a case of segregation of a natural hybrid, the crossing of which 

 took place in the season immediately preceding that in which the sporting 

 occurred. This explanation, however, is not satisfactory, for it is very 

 improbable that two separate cultures should have been accidentally 

 crossed in the same season with apparently the same second parent. 



From a bearded red-chaffed Squarehead wheat which had been 

 constant for several seasons, Riimker observed the production of a very 

 variable beardless sport under circumstances which excluded mixing of 

 sorts or natural hybridisation as explanations of the appearance of the 

 new form. 



The original bearded form was a selection from the progeny of the 

 hybrid Landwheat $ x Squarehead $ . 



I have had similar experience with Badger wheat (a selected bearded 

 Squarehead). 



Other examples are known among wheats, and Blaringhem states 

 that the hybrid Svanhals barley, constant when grown at Svalof, reveals 

 its hybrid origin when grown in Flanders and Picardy. 



These and similar sports are usually described as mutations, and 

 their new characters are assumed to be due to germinal variation arising 

 independently of segregation and recombination of the hereditary units 



